Seasonal body weight, body condition, and lactational trends in muskoxen

• Published in: Canadian Journal of Zoology
• Main Authors: White, R. G., Holleman, D. F., Tiplady, B. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1989
• Subjects: ovibos moschatus
• Online Access: http://dx.doi.org/10.1139/z89-162; http://www.nrcresearchpress.com/doi/pdf/10.1139/z89-162

Seasonal patterns of body weight, fat, protein, milk quality (dry matter content), and milk production rate were determined for three sexually mature female muskoxen (Ovibos moschatus) over three consecutive lactation periods. Females were allowed to graze in summer and had access to hay year-round. A high-protein pelleted ration supplemented this diet. Following calving in early May (1984, 1986) or June (1985), body weight remained constant throughout the summer, body fat declined for 3–5 weeks after calving, and body protein declined transiently during the latter period. Almost all annual gains in body weight and body fat occurred during the 6- to 8-week rutting period from mid-August to mid-October. High milk production (1.3–2.4 L/d) occurred 3 weeks post-calving, generally remained high for another month, and declined to 1.2 ± 0.15 L/d (mean ± SEM) just before the rut. A major decline in milk production, to 0.44 ± 0.050 L/d, occurred during the rut. Although milk dry matter increased 33% ± 4.3% during the rut, this increase was offset by the 60% ± 6.4% decline in milk production. All females successfully reproduced each year of the study and no evidence was found for a lactational anestrum. The hypothesis that gains in body weight must be made before the rutting period to maximize conception rate was rejected. This study highlighted the importance to lactating muskoxen of the late summer – early winter period for annual regain in body weight and body fat, which occurred concurrently with ovulation and conception.